The present invention relates to a system comprising a terminal coupled via a dial-up network to a gateway, the terminal comprises means for dialing the gateway and providing an identification of a second terminal connectable to said gateway.
To enable communication between existing telephony systems and emerging IP-based telephony xe2x80x98devicesxe2x80x9d (E.g. an Internet Telephony software package running on a PC) as well as the communication between existing telephony systems inter-connected via IP-based networks, so-called Telephony Gateways (hereafter called gateway(s)) are used. These gateways connect to an IP-based network (such as the public Internet and private Intranets) on one side and a telephone network (E.g. PSTN/ISDN/GSM) on the other side and provide the necessary conversion functions to transmit and receive voice-band and control data on either network.
Because of the differences in addressing structure on both sides of the gateway and because of the nature of some of the telephone networks, connections initiated from the telephone network side are usually set up by a two-step dialing process. First, a gateway is called and this gateway answers the call to obtain an identification of the second terminal, which can be constituted by additional addressing information for either an IP-based telephony device (E.g. an IP-address) or addressing information for the combination of a remote gateway and a remote (normal) telephone terminal. Second, the gateway uses this addressing information to attempt to set up a call to the xe2x80x98remotexe2x80x99 telephony device, which can either be an IP-based telephony device or a regular telephony device connected (directly or indirectly) to a remote gateway.
The problem with this approach is that a call is answered by the gateway, to obtain numbering information, before it is known whether the actual destination will answer the call. The caller will thus pay the bill for a call that may never exist and always pay for a duration that is longer than the actual call, when it takes place.
An object of the present invention is to provide a communication network according to the preamble in which the above problem is solved.
For achieving said object the communication network according to the invention is characterized in that the gateway is arranged for receiving the identification of the second terminal without answering the call.
When the gateway is arranged for receiving the identification of the second terminal before answering a call, no calling costs are incurred for transferring the identification of the second terminal. This can e.g. be done by using the signaling possibilities of ISDN. On ISDN interfaces complying with the ITU-T Q.931 Recommendation, calls are initiated by the transmission of a xe2x80x98setupxe2x80x9d message from the calling to the called party (from the calling user to the network to be precise). Such a xe2x80x98setupxe2x80x99 message contains mandatory information elements and may contain optional information elements. The xe2x80x98called party numberxe2x80x99, xe2x80x98called party subaddressxe2x80x99 and xe2x80x98keypad facilityxe2x80x9d information elements are three of these optional information elements. They (may) contain, when present, numbering and addressing information about the called terminal. It is observed that it is also possible to use ISDN interfaces which are derived from the Q.931 Recommendation, such as EURO-ISDN.
An embodiment of a communication network according to the invention is characterized in that the gateway is arranged for establishing communication with the second node, and in that the gateway is arranged for answering the call of the terminal after the second terminal has been contacted.
In this way it is obtained that the caller does not incur calling cost until the destination really answers the call, and that the behavior of the destination telephony device, as seen from the caller in the telephone network, is identical to the behavior of a destination telephony device that is located in and reached through the telephone network.